A small → galaxy cluster
of about 50 galaxies to which our
→ Milky Way galaxy belongs.
The Local Group occupies a volume of space nearly 10 million
→ light-years
across centered somewhere between the
→ Andromeda Galaxy (M31)
and the Milky Way, which are the dominant galaxies of the group; Andromeda
being the principal member. Both of these galaxies exhibit spiral
structures, and each is attended by a large family of satellite
→ dwarf galaxies. The Local Group
also includes a third spiral galaxy known as
→ Triangulum (M33), which is bound to Andromeda.
The remaining members span a range of → Hubble classification
types from dwarf spheroidal to Irr to Sb and Sc and cover a factor of 10 in
→ metallicity. The total mass of the Local Group is estimated to
be about 2 × 1012 solar masses, although this value is still uncertain
to within a factor of about 2. The velocities of the individual
galaxies of the Local Group are not particularly high. Therefore no
member is believed to be able to escape the group, which is thus
considered to be gravitationally → bound. Another
remarkable member of the Group is → IC 10.
See also: → local; → group.
